The Normal and the Enlarged Heart 



33 



10 (1970) 



The relation of the position of the normal and the enlarged 

 heart to the electrocardiogram. 



By ALFRED E. COHN and MILTON J. RAISBECK 



[From the Hospital of the Rockefeller Institute for Medical Re- 

 search, New York. X. Y.] 



It is well known that when the heart enlarges, it gives rise to 

 alterations in the electrocardiogram; the curve takes on one form 

 when the left ventricle is hypertrophic as in aortic insufficiency ; 

 it takes on an opposite form when the right ventricle is prin- 

 cipally involved, as in mitral stenosis. These electrical signs have 

 been useful in the clinic, but they have on occasion been mis- 

 leading, for we have obtained curves resembling those found in 

 enlarged hearts, in young soldiers and in civilians who, we 

 were quite certain, were not the subjects of disease. It occurred 

 to us that the position of the heart in the chest might be an 

 important contributing factor in producing the abnormal electro- 

 cardiograms. It is well known that changes in the curves are 

 possible as the result of respiratory movement: of the posture 

 of the body. An exaggerated instance occurs in dextrocardia, 

 as the result of which the electrocardiogram assumes the appear- 

 ance of a mirrored image of the usual curve. Having these ex- 

 periences to guide us we planned to ascertain in a systematic 

 manner precisely what was the effect of the position of the heart 

 in the chest. Obviously we could not rotate the heart in the 

 chest, but we could rotate the chest about the heart Our method 

 was as follows : Instead of taking the usual limb leads, we placed 

 electrodes at the apices of the largest equilateral triangle which 

 we could apply to the chest, the base of the triangle stretching 

 between the shoulders, the apex below the sternum. We assured 

 ourselves that the curves taken from these leads resembled 

 closly those from the limb leads. We proceeded then to rotate 

 this triangle through successive arcs of 40°, taking curves at each 

 new position from those points of the che-t wall to which the 

 apices of the triangle pointed. We photographed the three leads 

 simultaneously, using three galvanometers. By this means, we 

 did in effect rotate the chest about the heart. In normal in- 



